[asac]Band 4 frequency extension

[Stephane Guilloteau]

185 GHz is certainly quite far, and it would cause also problems for the LO
settings.
However, it would be good to check whether the H2S line at 168.8 GHz could
be reached.
It is only 6 GHz away from the current nominal upper band limit.
This would be useful for chemistry.

    Stephane

----- Original Message -----
From: "Tetsuo Hasegawa" <tetsuo.hasegawa at nao.ac.jp>
To: <asac at polaris.cv.nrao.edu>
Cc: <alma-pro at nro.nao.ac.jp>; <alma-shoi at nro.nao.ac.jp>
Sent: Wednesday, April 16, 2003 7:50 AM
Subject: [asac]Band 4 frequency extension


> Dear ASAC members,
>
> At the ASAC meeting in Grenoble, I was asked to consult with the
> Japanese frontend development team about the possibility of extension
> of the Band 4 frequency coverage up to 185 GHz to cover the water
> line.  Below is a quick reply from Yutaro Sekimoto, leader of the
> Japanese frontend group.
>
>
> Answer:
> Although it is an interesting development target, it would be very
> difficult to extend the RF frequency range of Band 4 that much, given
> the time schedule for fixing the design.  It is even more true
> because we are aiming at using 2SB mixers that relies on the
> waveguide technology.  Even if it becomes possible, significant
> degradation of the receiver noise temperature and image rejection
> ratio would be unavoidable.  Frequency coverage of the multiplier for
> LO would be another serious problem.
>
> For your reference, below is a list of fractional frequency coverage
> specified for the ALMA receiver bands.
>
> Band f(center)  f(low) - f(high) coverage
>
>   1    35 GHz    30 GHz -  40 GHz  29%
>   2    79 GHz    67 GHz -  90 GHz  29%
>   3   100 GHz    84 GHz - 116 GHz  32%
>   4   144 GHz   125 GHz - 163 GHz  26%  <<< current spec.
>   4*  155 GHz   125 GHz - 185 GHz  39%  <<< if extended
>   5   187 GHz   163 GHz - 211 GHz  26%
>   6   243 GHz   211 GHz - 275 GHz  26%
>   7   323 GHz   275 GHz - 370 GHz  29%
>   8   443 GHz   385 GHz - 500 GHz  26%
>   9   661 GHz   602 GHz - 720 GHz  18%
> 10   869 GHz   787 GHz - 950 GHz  19%
>
>
> With best,
>
> Tetsuo
> --
> _______________________________________________________________
> Tetsuo HASEGAWA, D. Sc.   <tetsuo.hasegawa at nao.ac.jp>
> ALMA-J Project Scientist
> Professor, National Astronomical Observatory of Japan
> 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
> Phone +81-422-34-3780 / FAX +81-422-34-3764
> _______________________________________________________________
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